1. Field of the Invention
The present invention relates to a mechanized excavating device for mounting on an auger crane to prepare a burial hole for utility pole and underbracing, and more specifically the hydraulic excavating auxiliary blades mounted at lower end of an extendable excavating screw unit is extendable and retractable by hydraulic pressure.
2. Description of the Related Art
Generally in the construction of power transmission and distribution lines and communication lines, utility poles are erected and electric and communication cables are installed on the poles. In this case, to respond the unbalanced tension of the electric and communication cables, a utility pole underbracing or guy wire is installed to prevent the utility pole from inclining or falling down. The utility pole underbracing is buried simultaneously with the utility pole after erecting the utility pole and excavating 0.5 m below the ground surface of the lower end of the utility pole. Next, to install the guy wire, excavation work for burial of the guy wire underbracing is carried out using man power or a machine. After that, guy wire underbracing is buried at the excavation point to be connected with the utility pole.
Normally, excavation work for installing such a utility pole underbracing or guy wire underbracing is done using an excavating screw fastened to an auger crane. Meanwhile, techniques for more achieving better quality and more efficient mechanized works are disclosed in prior art. For example, in Korean Patent Application No. 2005-126562 filed by the applicant of the present invention, as well as in Korean Utility Model Registration No. 0417120 and Korean Patent Application No. 2006-122020 are disclosed excavating screws for auger cranes having various types of retractable auxiliary blades.
However, because the excavating screws disclosed in these documents have a mechanism by which the auxiliary excavating blade is extended and retracted by manual rotation, many problems arise such as needing many workers, the difficulty of adjusting the auxiliary excavating blades, and the work time consumed to perform the adjustments.
So, an excavating screw in which auxiliary excavating blades of a type similar to the aforementioned are extended and retracted by hydraulic pressure is disclosed in Japanese Patent Laid-Open No. H13-73664. Since it is possible to remotely control the auxiliary excavating blades using hydraulic pressure in this excavating screw, it can be used economically and effectively. However, since the fluid transmission system is complicated in the auxiliary excavating blades having a hydraulic retracting means, actual application is difficult.
Meanwhile, both the excavating screw developed by the applicant of the present invention and the excavating screw with hydraulically extended and retracted auxiliary excavating blades can only be used for excavations of limited depth. Therefore, in the case of working on excavations deeper than the length of the excavating screw, an extendable excavating screw having an extension means should be used instead of the aforementioned excavating screw.
In an extendable excavating screw, an extension rod that can be inserted into and out of the excavating screw is inserted into the excavating screw. Since the total length of the excavating screw is varied according to the drawn-out length of the extension rod, excavation work is possible to deeper depths. Accordingly, if auxiliary excavating blades having a conventional rotation-type extending and retracting means are applied to an extendable excavating screw, operation is still difficult and cumbersome.
Therefore, the excavating screw used for deep excavation keenly requires auxiliary excavating blades and a hydraulic extending and retracting means to make more economic excavation possible.